Possessing a NAS SYNOLOGY (DS214 Play) that I can leave active H24, I would like to know if there is a version of BOINC that can work on this type of machine. Even if the computing power is not important, it can spend many hours. Thank you for your help.

No, you cannot install BOINC on a Synology NAS. It has a proprietary operating system on which one cannot install their own applications.

(And really, with a maximum operating temperature of 35 degrees centigrade you may not want to run 'heavy' calculations on the CPU that Seti would do. That translates into a lot of heat that the NAS isn't built for.)